Millikan cell

The value of Dm can be obtained by various methods such as image analysis, light scattering, Millikan cell, and mercury intrusion. 

The modified Millikan cell is superior to the classic one because it does not assume that the aggregates are symmetrical spherically and all carry the same chargeJ The modified cell is able to determine absolute mass and charge by photoemission method. 

The fractal dimension has also been determined from measurements of the terminal velocity Frs of a cluster and the electric field strength E required to balance the gravitational force [74]. This technique utilises the classical Millikan cell. A plot of log(Frs) against log( ) enables the fractal dimension to be computed from the gradient ... 

Nyeki, S. and Colbeck, 1.(1994). The measurement of the fractal dimension of individual in-situ soot aggregates using a modified Millikan cell technique. J. Aerosol Sci., 25, 75-90. 

Except for the theories of DERJAGUIN and co-workers [2.121], the theory in this regime has been developed for a stationary particle in a temperature gradient where the thermal force on a particle is exactly balanced by some external force such as an electric field for a charged particle, as in Millikan-cell experiments. The first approximate theory in this case was developed by EPSTEIN [2.131] who used the Navier-Stokes equation with a "thermal creep" boundary condition to obtain ... 

Several BGK analyses have been performed for the thermal-creep coefficient [2.99]. The only BGK analysis of the near-free-molecular regime thermal force (Kn. 1, Kn - 0) appears to be that of BROCK [2.136], Experimental Millikan-cell data were found by SCHMITT [2.97] and others to follow the relation... 

In a discussion of thermal-force theories it is necessary to address the problem of experimental data for the following reason. It has been known for some time that experimental thermal-force data determined by the Millikan-cell method [2.97, 98,137-139] differed from the data obtained by measuring the velocity of particle motion due to the thermal force (thermophoretic velocity) in various flow systems with different configurations [2.121,140,141]. 

DERJAGUIN and co-workers have offered the following explanation for the differences between their experimental data for the measured thermophoretic velocity and Millikan-cell measurements of thermal force. The values of thermophoretic velocity determined by DERJAGUIN and co-workers are usually from two to four times the corresponding values obtained by the Millikan-cell method. DERJAGUIN and coworkers have claimed that there are uncontrolled convection currents in the Millikan cell and cite the experiments of PARANJPE [2.142] who observed convection currents in the central portion between two parallel plates when the ratio of plate diameter to separation between the plates was less than 5 or 6. There are several reasons to discount this explanation. GIESEKE [2.139] has published experimental... 

The Millikan oil-drop experimenL one of die classical experiments of physics in the early 1900s, used the preceding electrostatic principles to measure the charge of an individual electron. The apparatus used, called a Millikan cell, is shown in Fig. 15.1. A spherical, submicrometer-sized particle (an oil droplet) is introduced between two horizontal parallel plates. The potential difference between the plates can be carefully controlled. The particle is illuminated by a beam of light between the plates and observed by a horizontal microscope positioned perpendicular to the... 

What voltage is required to just balance a singly charged (negative) 0.8-pm-diameter particle in a Millikan cell The plate spacing is 5 mm and particle density is 1000 kg/m [1.0 g/cm ]. 

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